Ripped, torn, scarred, aching flesh on the hands as a result of mechanical work. Usually the result of a slipped wrench or a screw that comes loose more easily than expected.

When working in a tight space underneath your car without much room to move and you are trying to remove a hex nut, next thing you know your wrench slips with a metallic noise and you've smashed your hand into the body of the car resulting in a busted knuckle. And it hurts like a motherfucker.